I. Field of the Invention
The present invention relates generally to medical devices and, more particularly, to a binocular indirect ophthalmoscope.
II. Description of the Prior Art
Binocular indirect ophthalmoscopes, hereafter called ophthalmoscopes, are used by ophthalmologists for examining the eye and particularly the retina of the eye. The previously known ophthalmoscopes include a housing having two eyepieces, one for each eye. The housing is then removably secured to the head of the user by a head strap so that one eyepiece is aligned with each eye of the user.
An optical system, typically comprising a pair of mirrors and a prism, is also contained within the ophthalmoscope. This allows for directing reflected light from the patient's eye outwardly through the housing and then through each eyepiece. This constitutes the viewing axis for the ophthalmoscope.
In order to provide sufficient illumination through the pupil of the eye so that the retina can be seen, these previously known ophthalmoscopes include a tungsten or halogen light bulb contained within the housing between and above the eyepieces. The light from the light bulb is then reflected by a mirror or other optical means along a variable illumination axis and thus parallel to the viewing axis of the ophthalmoscope.
These previously known ophthalmoscopes, however, suffer from a number of disadvantages. One disadvantage is that the light bulb becomes quite hot after prolonged use which correspondingly heats the housing of the ophthalmoscope. In doing so, the ophthalmoscope becomes uncomfortably warm for the user. The light source must have a heat sink which adds weight to the ophthalmoscope. This added weight can cause fatigue or stress in the viewer's cervical spine.
A still further disadvantage of the illuminating means for these previously known ophthalmoscopes is that the light bulbs are relatively fragile. As such, the filaments within the light bulbs are prone to breakage from even small impacts to the ophthalmoscope housing.
Lastly, the ophthalmoscope must be removed from the examiner's head when the examiner wishes to begin operating on the patient's eye. During the course of an operation the ophthalmoscope is often placed back on the examiner's head and removed again. The frequent removal and replacement of the instrument is necessary because separate loupes are required for magnification of the eye during surgery.